igneous
Granite Cobble
Phaneritic plutonic rock (dominated by Quartz, Feldspar, and Mica)
Hardness: 6-7 Mohs; Color: Mottled gray, black, and orange-pink; Luster: Dull (weathered) to vitreous (crystals); Crystal structure: Granular/Phaneritic; Specific gravity: 2.6-2.7
- Hardness
- 6-7 Mohs
- Color
- Mottled gray, black, and orange-pink
- Luster
- Dull (weathered) to vitreous (crystals)
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Physical properties
Hardness: 6-7 Mohs; Color: Mottled gray, black, and orange-pink; Luster: Dull (weathered) to vitreous (crystals); Crystal structure: Granular/Phaneritic; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the slow cooling of silica-rich magma deep underground. This specific specimen appears to be a water-worn cobble or pebble, showing rounding and surface oxidation (iron staining) from transport in a river or glacial environment.
Uses & applications
Raw granite is used for construction aggregate, dimension stone, and countertops. As a small field-collected cobble, its primary use is geological study or as a decorative garden stone.
Geological facts
Granite is the primary component of the Earth's continental crust. The pink-orange hues in this specimen are likely due to orthoclase feldspar or secondary iron oxide staining.
Field identification & locations
Identify in the field by its 'salt and pepper' appearance and visible interlocking crystals. Common in mountain ranges and glacial till across North America and Europe.
